1. Field of the Invention
This invention relates to shock absorber struts, and more particularly to a very large heavy strut means wherein inner and outer assemblies can rotate independently in at least two different directions.
2. Description of the Prior Art
Heavy off-road haulage trucks, which are designed to carry loads in the range of from 35 to 220 tons over rough terrain, are designed to employ some sort of shock absorber strut means. Such strut means are massive in size, for example, a strut means for a 150 ton hauler weighs in the range of 1,100 to 1,200 lbs. and is approximately 71/2 ft. long and 14 inches in diameter. A substantial number of such struts employ hydraulic principles to absorb the shock. Characteristically, they leak and require frequent servicing. Invariably they must be removed entirely from the vehicle and taken to a repair shop, for example, for servicing, which, as appreciated because of their size, is very difficult. The present inventor, in an earlier development, as described in U.S. Pat. No. 4,756,512, issued July 12, 1988, to Robert S. Toms, Jr., overcame the deficiencies associated with struts employing hydraulic principles by designing a suspension strut using elastomer material pads assembled in stacks, as sold by Miner Enterprises, Inc., of Geneva, Illinois, under the trade name "TecsPak", and more fully described in U.S. Pat. No. 4,198,037, issued Apr. 15, 1980, to Anderson. The strut assembly comprises a pair of telescoped tubes housing therein a stack of pads, each having a central opening for admitting a steel guide rod. The pads are separated from each other by intervening steel plates. It has been determined that occasionally, the suspension strut, when subjected to compression, will compress the elastomer material to such an extent that the size of the central openings in some of the pads will be decreased by the flow of the elastomer material, which then applies a compressive force to the guide rod, thereby rendering it less effective in providing a cushioning force. Furthermore, such gripping of the guide rod by the pads causes wear in the pads by enlargement of the central openings to such an extent that the guide rod loses its function of maintaining the pads concentrically in the telescoped tubes.
It is, therefore, a prime objective of the present invention to provide shock absorber strut means using pads which are not subjected to mechanical deterioration as the pads move along the guide rod.
Another object of the invention is to use a pad assembly comprising a pad made from resilient mat.RTM.rial, a steel plate, and a bearing, all arranged as a single unit and substantially isolating the resilient material from contacting the guide rod.
A further object of the invention is to provide an assembly of two different types of pad assemblies in a shock absorber strut to provide a predetermined amount of damping.